The field of this invention comprises selfcontained wheeled power units for use in the field, primarily for manhole operation. The problems of the men doing underground maintenance and construction work are varied and the equipment they need is manifold. Some of the problems encountered require all or many of the following functions and sources of power and the like:
Electricity. Many of the apparatuses which are used underground comprising motors, drills, soldering irons, welding equipment, testing instruments and the like are operated by electricity. This may be 120 volts or 240 volts and may be a.c. or d.c. The power may be as great as several horsepower. Ideally a service apparatus should furnish any of these and should do so with considerable control and safety.
Pumping. Manhole work is done underground where seepage and moisture readily accumulate and where leakages are sometimes the cause of the problems to be solved. The water must be pumped out and the working area kept dry by means of a powerful pump which is capable of handling trash and gravel normally encountered underground.
Compressed Air. Many jobs in manholes require the use of compressed air for multiple purposes. Air is needed to drive some equipment such as hammers and working tools. In explosive atmospheres air is the only power which can be used. Air is used for cleaning and testing, especially in the case of cable splices.
Ventilation. Workmen in manholes require ventilation, and the equipment which usually accompanies a job of this kind includes some means for supplying at least the ambient air to the manhole. In cold weather this air is not comfortable and would be best heated.
The above indicates that the equipment which must accompany a serviceman when he is going to work in a manhole is not simple. To supply all of the above requires considerable equipment and the logistics involved have heretofore been a substantial headache. The equipment was brought out to the site in multiple vehicles and where not accompanied by a truck which was tied down to the site, was scattered around the manhole presenting a rather undesirable appearance. To keep the equipment going and controlled required much maneuvering and adjusting. The expense of tying up a truck was great.
Since manhole work must be done without using any outside sources of power, a unit which can serve all of the purposes mentioned above and those related and not specifically detailed, must be self-contained. Prime movers for such units are normally internal combustion engines, with bottled fuel engines being preferred because handling their fuel is safer and the amount of emissions which are undesirable are less. Bottled fuel usually comprises propane, normally bottled under great pressure to substantial liquidity and injected into the engine as a gas. One problem with bottled fuel is that in cold weather the fuel does not readily gasify. The invention provides means for keeping the fuel bottles warm in cold weather.
All of the requirements of a unit for manhole work can be met with equipment which can be gathered together and mounted on a truck, but the cost would normally be excessive. Trucks are not made for specific operation as manhole vehicles and modification from standard structures would be prohibitively expensive.
The invention achieves all of the requirements of a comprehensive manhole vehicle at a great saving and in addition provides novel functions through the use of structures which enable the maximum of utility to be extracted from the equipment used. The actual vehicle per se has a novel construction. In addition, highly efficient and novel heat exchange apparatus is utilized.
The vehicle of the invention is totally portable, being equipped to be towed on its own wheels by a suitable truck.